This is just a functionality thing “Pixel account ID to link sites for paid advertising - with FB or Insta - tagged product or brand endorsement” The only fees you’lll pay to facebook are - when you access “meta business suite” for a boosted post of one of your tagged items in your products / items library *
Depending how you set your store up to work with Meta alters the costs involved - If you select checkout on your own website (square) in the Meta business suite you will only pay square fees on the sale as they have redirected the purchaser to your website.
